diff --git a/src/DI/Config/Loader.php b/src/DI/Config/Loader.php
index d18d3516f..9659de74a 100644
--- a/src/DI/Config/Loader.php
+++ b/src/DI/Config/Loader.php
@@ -56,7 +56,7 @@ public function load($file, $section = null)
 		if (isset($data[self::INCLUDES_KEY])) {
 			Validators::assert($data[self::INCLUDES_KEY], 'list', "section 'includes' in file '$file'");
 			foreach ($data[self::INCLUDES_KEY] as $include) {
-				if (!preg_match('#([a-z]:)?[/\\\\]#Ai', $include)) {
+				if (!preg_match('#([a-z]+:)?[/\\\\]#Ai', $include)) {
 					$include = dirname($file) . '/' . $include;
 				}
 				$merged = Helpers::merge($this->load($include), $merged);